Glucuronide conjugation is a major route of drug metabolism and provides living organisms with a way to eliminate lipid-soluble chemicals to which they are exposed. Hepatic microsomal UDP-glucuronyltransferases (UDPGTs) catalyze the formation of glucuronides. Our laboratory has isolated a number of these proteins which are important in the conjugation of xenobiotics and endogenous substances. Determination of hepatic lobular localization and distribution of p-nitrophenol UDP-glucuronyltransferase (PNP-UDPGT), 17Beta-OH steroid UDPGT and 3Alpha-OH steroid UDPGT by immunohistochemical analyses is planned. Using specific antibodies, studies will demonstrate the changes in distribution produced by various agents such as 3-methylcholanthrene. In addition, liver, gastrointestinal tract, lung and kidney will be studied from Wistar rats possessing high levels of 3Alpha-OH steroid UDPGT (HA) and low levels of 3Alpha-OH steroid UDPGT (LA). These studies will allow for an understanding of the role of cellular heterogeneity in glucuronidation. Experiments will reveal N-terminal amino acid sequences of PNP-UDPGT, 17Beta-OH steroid UDPGT and 3Alpha-OH steroid UDPGT. In addition, the genetic regulation of expression of these transferases in untreated rat livers and in livers of rats treated with 3-methylcholanthrene will be studied. The mechanism of genetic variance for 3Alpha-OH steroid UDPGT will be studied in HA and LA Wistar rats. Purification of morphine and digitoxigenin monodigitoxoside UDPGTs will be performed and, then, these enzymes will be studied further as described for other UDPGTs. Purification and characterization of human liver UDPGTs will be performed. Experiments on phospholipid requirements, N-terminal amino acid sequences and the genetic regulation of expression of human liver UDPGTs are planned. Finally, the role of cellular heterogeneity in human tissues will be explored using immunohistochemical methods. Thus, how and where glucuronidation occurs can be probed and understood.